Heat exchangers included in refrigerating devices, air conditioning devices, heat pumps, etc., generally include fins that are arranged with predetermined intervals therebetween and a heat transfer pipe secured such that the heat transfer pipe extends through each fin. The heat transfer pipe serves as a part of a refrigerant circuit in a refrigeration cycle device and allows refrigerant (fluid) to flow therethrough.
Grooves are formed on an inner surface of the heat transfer pipe so that a plurality of groove portions and a plurality of projections extend in a circumferential direction and an axial direction of the heat transfer pipe 20. The refrigerant that flows through the heat transfer pipe undergoes a phase change (condensation or evaporation) as a result of heat exchange with air or the like outside the heat transfer pipe. To increase the efficiency of the phase change, the heat transfer performance of the heat transfer pipe has been improved by, for example, increasing the surface area inside the pipe or utilizing a fluid agitation effect provided by the groove portions or an effect of holding a liquid film between the groove portions provided by capillary action of the groove portions (see, for example, Patent Literature 1).